'69 stepside tailgate trunion... bushing? How's this work.

[blf]

So, the bolt on the driver's side of my tailgate apparently rattled loose and fell out somewhere.

I have the bushing (?) from that side..

3 questions...

1) Anyone know what size bolt do I need to replace the missing one?
2) Do I just use a regular washer (looks like a regular washer on the other side.
3) What's the slot for? Just holding it from turning or does something pin in there?

I'm not interested in buying a new set of bushings today, thanks.